In general, a radio communication system uses a specified frequency band for transmitting and receiving data. For example, in IEEE 802.11g widely known as the U.S. standard for wireless Local Area Network (LAN), the frequency band from 2.4 GHz to 2.47 GHz is used, and the maximum transmission rate of 54 Mbps is attained in a communication distance of 50 to 100 m. However, the demands from general users to data have been increasing year after year, and it has been strongly expected to download music data and High Definition video data as well as High Definition picture data to user's portable equipments in a short time. One of technologies to meet this demand is Ultra Wide Band (UWB) radio communications. As for the UWB radio communications, since the U.S. Federal Communications Commission permitted the commercial use of UWB in April, 2002, many organizations have been promoted its research and development activities.
In such UWB radio communications, descriptions on local oscillation signal generating circuits for the UWB radio communications are found in, for example, A Ismail et. al., “A 3.1 to 8.2 GHz Direct Conversion Receiver for MB-OFDM UWB Communications”, (U.S.), IEEE Solid-State Circuits Conference, 2005 Collected Papers, lecture No. 11.5, pp. 208 to 210 (Non-Patent Document 1), C-F. Liang et al., “A 14-band Frequency Synthesizer for MB-OFDM UWB Application, (U.S.), IEEE Solid-State Circuits Conference, 2006 Collected Papers, lecture No. 6.7, pp. 126 to 128 (Non-Patent Document 2), Japanese Patent Application Laid-Open Publication No. 2005-175698 (Patent Document 1), Japanese Patent Application Laid-Open Publication No. 2005-198304 (Patent Document 2), Japanese Patent Application Laid-Open Publication No. 2005-129993 (Patent Document 3), Japanese Patent Application Laid-Open Publication No. 2005-39827 (Patent Document 4), and others.
In the Non-Patent Document 1, after an oscillation frequency fREF is generated by a single-tone signal generator using an oscillator configured of a resonant circuit including an inductor and a capacitor that can generate four-phase signal, signals of a plurality of frequencies are generated by use of a plurality of divide-by-2 frequency divider circuits and Single Sideband Mixers (SSB Mixers).
In the Non-Patent Document 2, two single-tone signal generators are disposed, and a frequency of an integral multiple of 528 MHz and a frequency of a decimal multiple thereof are generated simultaneously, and then, three SSB mixers are used simultaneously to repeat adding and subtracting of frequencies, thereby generating a sub-band center frequency.
In the Patent Document 1, in a high speed frequency hopping local generator, a frequency to become reference is generated and divided into four, and then, signals of a plurality of frequencies are generated by use of a plurality of dividers such as a divide-by-5 frequency divider, a divide-by-3 frequency divider, a divide-by-4 frequency divider, and a divide-by-2 frequency divider.
In the Patent Document 2, in a communication system in which data are transmitted and received by use of a UWB formed by including at least two frequency groups consisting of at least two single-tone frequencies, a plurality of single-tone frequencies are generated by use of one local oscillator and one PLL.
In the Patent Document 3, in a frequency synthesizer that synthesizes two or more frequencies to obtain a new frequency, the single-tone frequency is divided by two to obtain a sampling frequency, and further it is divided by two, divided by four, and divided by eight to generate a plurality of frequencies.
In the Patent Document 4, in an SSB generator that generates a carrier wave by use of one local oscillation signal and at least two intermediate frequency signals, group signals formed of signals that have performed phase shift and those have not performed phase shift for each frequency are generated, and one group signal is selected among them and transmitted to the SSB generator.